The Colour Purple, Help

I have not been albe to make purple, in anything, fondant, buttercream even gumpaste ??? I use Wiltons violet and Americolours violet, purple, electric purple and even airbrush purple sheen. All either never go purple or quickly turn blue as it dries. What do you use ? I see so many beautiful creations with lovely shades of purple. I need to know, please HELP